Plunger for nozzle assembly

ABSTRACT

The present invention is directed toward a plunger provided for use in a nozzle assembly. The nozzle assembly includes an internal chamber with an outwardly tapered portion at one end thereof. The plunger includes a plurality of outwardly curved prongs or legs which mate with an inwardly tapered portion of the internal chamber in order to allow the piston of the injector to be released from the plunger. As a result, the plunger may be removed from the injector when the nozzle assembly is removed therefrom. This plunger may include a frangible portion so that, upon firing, a first driving member of the plunger breaks away from a second driving member of the plunger. As a result of this frangible connection, the first driving member remains lodged in a distal portion of the chamber to prevent reuse of the nozzle assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.08/608,799, filed on Feb. 29, 1996, now U.S. Pat. No. 5,643,211.

FIELD OF THE INVENTION

The present invention generally relates to a nozzle assembly for aneedleless fluid injection apparatus. More particularly, the presentinvention relates to a locking mechanism to aid in the prevention ofaccidental disengagement of the nozzle assembly from the injectionapparatus and to a plunger for use in a nozzle assembly.

BACKGROUND OF THE INVENTION

Needleless hypodermic injection devices have been known and used in thepast. These devices typically use spring or compressed gas drivenplungers to accelerate a fluid at a velocity sufficient to pierce theskin and enter the underlying tissues.

Since at least the 1980s, the use of needleless injectors has becomemore desirable due to concerns over the spread of AIDS, hepatitis andother viral diseases caused by the possibility of accidental needle"sticks" from the conventional syringe and needle. Needleless injectorsremove apprehensions of health care workers and are superior ineliminating accidental disease transmission.

A number of different needleless injectors are known including U.S. Pat.Nos. 5,062,830 to Dunlap, 4,790,824 to Morrow et al., 4,623,332 toLindmayer et al., 4,421,508 to Cohen, 4,089,334 to Schwebel et al.,3,688,765 to Gasaway, 3,115,133 to Morando, 2,816,543 to Venditty, etal., and 2,754,818 to Scherer. These injectors typically include anozzle assembly, which includes a medication holding chamber and aplunger. The chamber has an orifice through which a jet of medication isforced out of the chamber using the plunger actuated by a piston whichis typically connected to some type of energy source.

Due to the high velocity of the jet and/or the high pressure of theenergy source created by the typical needleless injector, it has beenfound that nozzle assemblies have a tendency to disengage during firingof the energy source. This can result in the creation of a dangeroussituation, particularly if the nozzle assembly acts as a projectile. Thetendency for this to occur has been found to be more pronounced withbayonet mounted nozzle assemblies, as shown in U.S. Pat. No. 5,599,302to Lilley et al. However, this problem may also exist with conventionalscrew-type mounts. Thus, there is a need for a locking mechanism whichwill deter the nozzle assembly from unexpectedly releasing from theinjector body.

Nozzle assemblies for injectors typically include a plunger installedinside of the internal chamber of the nozzle assembly for moving themedicament from the nozzle assembly. After expelling the medicament, itis desirable to remove the nozzle assembly from the injector for eithersterilization or disposal.

A problem associated with nozzle assemblies is the tendency for theplunger to remain attached to the piston of the injector after theenergy source has fired. Thus, when either a disposable or reusablenozzle assembly is removed from the injection apparatus, the plunger mayremain connected to the piston. In order to avoid possiblecontamination, the plunger must be removed from the injector for eitherdisposal or resterilization. It is often difficult to remove theseplungers and sometimes necessary to destroy them in the process ofremoving them. It is, therefore, desirable to provide a plunger whichwill allow easy removal from the injection apparatus and which may beremovable with the nozzle assembly.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a plunger which isslidingly movable within a fluid chamber. The plunger is used to expelfluid out of or draw fluid into the chamber by moving the plungerrelative to the chamber. The plunger includes first and second drivingmembers which have respective end and base portions. The end and baseportions are retained in spaced relation by a frangible connectiontherebetween. The second driving member is spaced relative to the firstdriving member by a gap. The frangible connection is broken when a forcesufficient to break the connection is applied to the second drivingmember in a direction toward the first driving member. When such a forceis applied, the second driving member moves across the gap toward thefirst driving member to urge the first driving member toward an end ofthe chamber to expel fluid. After moving the first driving member to anend of the chamber, the second driving member is then moved away fromthe first driving member. When the second driving member is moved, thefirst driving member remains in the chamber to prevent reuse of theplunger.

The plunger is cylindrical and the first and second driving members meetto define the frangible connection. The frangible connection includes atleast a portion which extends across the diameter of the plunger. Thefrangible connection may be disposed perpendicular to the planes formedby the surfaces of the end portions of the first and second drivingmembers. The frangible connection may be spaced radially relative to thelongitudinal axis.

The end and base portions of the first and second driving members faceeach other and are joined by the frangible connection. The frangibleconnection extends from the second driving member to connect the endportions of the driving members. When the frangible connection is brokendue to a force applied to the second driving member, the second drivingmember moves across the gap toward the first driving member. The baseportion of the second driving member contacts the end portion of thefirst driving member. At the same time, the end portion of the seconddriving member contacts the base portion of the first driving member.This results in urging the first driving member towards the end of thechamber.

In a second embodiment, the plunger is slideably movable in a chamberand includes a body member and a plurality of outwardly curved prongs.The body member has a distal end and a proximal end. Fluid is expelledout of and drawn into the chamber through the distal end. The prongs arelocated at the proximal end and are operatively associated with a forcegenerating component.

The chamber may also have proximal and distal ends with an outwardlyflared portion adjacent the proximal end. This outwardly flared portionis configured and dimensioned to receive the outwardly curved prongs toallow for release of the force generating component from the prongs.

The prongs may also include a lip on an inner surface and a ridge on anouter surface. When the ridge is used, the chamber outwardly flaredportion also includes an annular groove for receiving the ridge. Thelips are used to engage the force generating component when the prongsare positioned in the chamber.

In another embodiment of the present invention, a nozzle assemblyadapted for use with an injection device includes a chamber, a forcegenerating component, and a plunger, such as that of the first or secondembodiment. The chamber holds fluid and has an orifice for passage ofthe fluid at one end. The force generating component is for generatingforce to expel the fluid out of or draw fluid into the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention are disclosed in theaccompanying drawings, wherein similar reference characters denotesimilar elements throughout the several views, and wherein:

FIG. 1 is an elevated side view of an injector nozzle incorporating thelocking features of the present invention;

FIG. 2 is a perspective view of a retaining element for use with aninjector nozzle which incorporates the locking feature of the presentinvention;

FIG. 3 is a cross-sectional side view of an injector body including aretaining element for receiving a nozzle incorporating the lockingfeatures of the present invention;

FIG. 4 is an elevated top view of an injector nozzle incorporating thelocking features of the present invention;

FIG. 5 is a cross-sectional side view of the injector nozzle shown inFIG. 1;

FIG. 6 is an end view of the tip of the injector nozzle showing theindicating tabs on either side;

FIG. 7 is an exploded cross-sectional view of the bayonet mounts of thenozzle assembly;

FIG. 8 is an elevated top view of the retaining element of the presentinvention shown in FIG. 2;

FIG. 9 is an elevated side view of the retaining element shown in FIG.2;

FIG. 10 is a cross-sectional view of the retaining element taken alongplane 10--10 as shown in FIG. 8;

FIG. 11 is a cross-sectional view of the retaining element taken alongplane 11--11 as shown in FIG. 8;

FIG. 12 is a partial cross-sectional view of one embodiment the plungerof the present invention;

FIG. 13 is a cross-sectional view of one of the prongs on the plunger ofFIG. 12;

FIG. 14 is a proximal end view of the plunger shown in FIG. 12;

FIG. 15 is a cross-sectional view of the plunger at area 15--15 as shownin FIG. 12;

FIG. 16 is a cross-sectional view of the plunger installed in theinternal chamber of the nozzle assembly after the injector has beenfired and the piston of the injector has been withdrawn;

FIG. 17 is a partial cross-sectional view of another embodiment of theplunger of the present invention;

FIG. 18 is a cross-sectional view of one of the prongs on the plunger ofFIG. 17;

FIG. 19 is a proximal end view of the plunger shown in FIG. 17;

FIG. 20 is a cross-sectional view of the plunger at area 20--20 as shownin FIG. 17;

FIG. 21 is a cross-sectional view of the plunger of FIG. 17 installed inthe internal chamber of the nozzle assembly prior to loading the chamberwith medicament;

FIG. 22A is a cross-sectional view of the plunger of FIG. 17 installedin the internal chamber of the nozzle assembly after the injector hasbeen fired;

FIG. 22B is a cross-sectional view of the plunger of FIG. 17 installedin the internal chamber of the nozzle assembly after the injector hasbeen fired, the nozzle assembly has been rotated out of locked positionand the piston of the injector is about to be withdrawn; and

FIG. 23 is an exploded view of area 23--23 from FIG. 22 of the proximalend of one of the legs of the plunger in mating arrangement with theinternal chamber of the nozzle assembly as the piston of the injector isbeing withdrawn.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exterior of a nozzle assembly 10 is shown in FIG. 1 with severalembodiments of the locking mechanism of the present invention installedthereon. A retaining element 20, or retaining ring, is shown in FIG. 2.The present invention utilizes a nozzle assembly 10 incorporating alocking mechanism in conjunction with a retaining element 20 in aninjector 30. This combination will deter unexpected disengagement of thenozzle assembly 10 from the injector 30.

An injector 30 is shown in FIG. 3 with the retaining element 20 disposedinside of injector 30 near the distal end thereof. The nozzle assembly10 is typically installed in a distal end of injector 30. The injector30 is shown for illustration purposes only since the present inventionis not intended to teach one of ordinary skill in the art how to make aninjector. For this purpose, U.S. Pat. No. 5,599,302 to Lilley et al. maybe utilized for an injector with a gas spring energy source, thecontents of which is incorporated herein by reference. It should benoted that any type of injector may be utilized with the lockingmechanism of the present invention. Further, any type of energy sourcemay be utilized with the present invention, such as a gas spring, coilspring, or compressed gas. Also, the nozzle assemblies contemplated foruse with this invention may be either disposable or reusable.

As used in this application, the terms distal or front shall designatethe end or direction toward the nozzle assembly 10 of the injector 30.The terms proximal or rear shall designate the end or direction towardthe power unit 32. The term longitudinal designates an axis X--Xconnecting nozzle assembly 10 to power unit 32, and the term transversedesignates a direction substantially perpendicular to the longitudinaldirection including arcs along the surface of injector 30.

Referring again to FIG. 1, a nozzle assembly of the present invention isdepicted. Nozzle assembly 10 has a tubular body and includes a tip 12 atthe distal end and a tail 14 at the proximal end. The nozzle assembly 10also includes a plurality of threads 16 disposed on the body of thenozzle assembly 10 between the tip 12 and tail 14 and a transitionportion 18 located between the threads 16 and the tip 12.

The threads 16 are preferably in a partial helix pattern around thecircumference of the nozzle assembly tubular body 10. Threads 16, whenin the partial helix pattern, form rib segments 16. The rib segments 16are preferably canted at an angle β which preferably ranges from about0° to 7° with a range of 0° to 3° being most preferred, as shown inFIG. 1. Angle β is measured from a plane drawn perpendicular to thelongitudinal axis X--X of nozzle assembly 10. Rib segments 16 are spacedapart relative to each other and are preferably at a predeterminedpitch. Pitch determines the rate of axial travel of the nozzle assemblywhen the rib segments are rotated by defining the spacing between therib segments 16. Pitch is preferably about 0.08 inches per thread, butcan vary over a range of about 0.04 to 0.2 inches per thread. It hasbeen found that the nozzle assembly is more likely to disengage orunscrew when pitch and angle β is larger, such as at a 7° angle and a0.1 inches per thread pitch. Thus, a larger β and pitch results in agreater likelihood of disengagement.

The tail 14 is for insertion into a distal end 34 of an injector 30.When the tail 14 is inserted into the injector body 30, the rib segments16 are received by corresponding grooves 36 in the interior of theinjector 30 so that the rib segments 16 and tail 14 of the nozzleassembly 10 are housed within the injector after insertion and rotation.When the ribs have been inserted and rotated properly, they are then intheir final position.

The rib segments 16, as shown in FIG. 1, are of the bayonet mount type.Conventional screw type threads may also be used. When the tail 14 andrib segments 16 are inserted into the injector 30, the nozzle assembly10 is rotated in order to engage the bayonet mount rib segments 16 withthe grooves 36 in the interior of the injector 30. The transitionportion 18, being of a larger diameter than the rib segments 16 and tail14, then rests at the distal end of the injector 30.

Referring to FIGS. 1, 4, and 7, the preferred rib segments 16 forconnecting to the injector 30 are of the quarter turn variety, meaningthey are positioned about substantially 1/4 of the circumference of thebody on one side and about 1/4 of the circumference of the body on theopposite side. It is preferred that the lead or proximal-most thread 17be wider in cross-section than the other threads. It is also preferredthat the remaining rib segments 16 be of the same cross-sectional width,although this is not required. Tooth 17 is wider than the remainingteeth in order to insure that nozzle assembly 10 is fully inserted intothe injector 30 prior to being rotated into locked position. Since thegrooves 36 in injector 30 are preferably sized to receive rib segments16, the proximal-most groove for receiving rib segments 16 is preferablywider than the other grooves. Thus, unless the nozzle assembly 10 isfully inserted into injector 30, it is difficult, if not impossible, torotate the nozzle assembly 10 into a locked position.

In addition, the distal-most thread 19 is preferably a half-thread. Byhalf-thread it is meant that the thread 19 is positioned aboutsubstantially 1/2 the circumference of the nozzle assembly 10. Thisthread 19 interferes with the distal-most ridge 21 associated withgrooves 36. Since grooves 36 are preferably disposed on oppositeinternal sides of injector 30, the half thread 19 is not able to pass byridge 21. In this manner, nozzle assembly 10 is deterred from beinginserted too far into the distal end of injector 30. The combination ofwide tooth 17 and long tooth 19 helps to insure the nozzle assembly 10is properly positioned into injector 30 prior to firing.

Further, as shown in FIG. 7, it has been found that the cross-sectionaldimension of rib segments 16 is important, although not critical, to thepresent invention. The preferred type of teeth 16 for the bayonet mountare typically referred to as buttress threads. These threads arepreferred where the threads are required to receive a large longitudinalload. Buttress-type threads also help to deter the rib segments 16 fromtwisting when under load. As shown in FIG. 7, the buttress threads 16preferably have a distal edge which is preferably substantiallyperpendicular to the longitudinal axis X--X (FIG. 5), a flat top whichis substantially parallel to the longitudinal axis X--X, and an angledproximal edge. The slope of distal edge is preferably within about 100of the perpendicular. The angled proximal edge is preferably 290, asmeasured from the plane of the flat top surface, but can preferably varyover a range of about 20 to 40°.

As depicted in FIGS. 1, 4, and 5, nozzle assembly 10 has an elongatedbody defining a chamber 40 which communicates with an orifice 42 at thedistal end of the nozzle assembly 10. Fluid such as liquid medicamentcan pass into the chamber 40 through orifice 42. Also fluid can pass outof the orifice 42 during the injection process. The body of the nozzleassembly 10 is generally cylindrical and, at its distal end, has aconical tip 44 with the orifice 42 positioned centrally in the tip 44preferably along the longitudinal axis X--X of nozzle assembly 10. Acylindrical collar 46 extends proximally from the rear end of conicaltip 42. Following the collar 46 in the proximal direction is thetransition portion 18, which may be utilized to connect the nozzleassembly 10 to an adapter (not shown), a cap (not shown), or any otherdevice which is desirable to attach to the tip end of a nozzle assembly.Transition portion 18 preferably includes a plurality of depressions 48which are configured and dimensioned for engaging with another device,of the type discussed above. The transition portion 18 also preferablyincludes an indicating tab 50 which extends outwardly on either side ofthe transition portion 18.

Indicating tab 50 will be discussed more fully below.

The depressions 48 on the transition portion 18 may be of any type whichwill allow connection of the nozzle assembly 10 to another device.Following the transition portion 18 in the proximal direction are therib segments 16 which are followed by the tail portion 14. The tailportion 14 includes the locking mechanisms of the present invention.

It has been found that, because of the high velocity jet created whenthe injector 30 is fired, the nozzle assembly 10 has a tendency todisengage by unscrewing during firing. This effect is more pronouncedwhen bayonet mounts, as shown in FIGS. 1 and 4, are used, but can alsobe found to exist where conventional screw type mounts are used. It isdesirable to have a mechanism for inhibiting or locking the injector inorder to avoid unintentional or accidental disengagement of the nozzleassembly. The present invention is directed to several mechanisms forlocking the nozzle assembly in place during firing.

A first embodiment of the locking mechanism is found in the use of astud 52 which protrudes from the external circumference of the tailportion 14 of the nozzle assembly 10. Two studs 52, as shown in FIG. 5,are preferred, although a single stud 52 may be used effectively. Thetwo studs are preferably positioned on opposite sides of the tail 14.When the tail 14 is inserted into the injector 30, the stud 52 engagesin a recess 54 in the interior of the injector 30. This recess 54 may beprovided by the retaining element 20, as will be discussed in greaterdetail below.

It is preferred that, when the tail 14 and rib segments 16 are insertedinto the injector 30 and rotated to turn the rib segments 16 into thegrooves 36, the stud 52 is allowed to travel in the recess 54 until itreaches a detent 56. The stud 52 preferably travels axially at the samerate as the rib segments 16. When the stud 52 has traveled to the finaldetent, the nozzle assembly 10 has been entirely screwed into theinjector 30 into a final locked position. As the stud 52 reaches thefinal locked position, the user preferably receives positive feedbackthat the nozzle assembly 10 has been locked in. This positive feedbackmay be a clicking noise or tactile feedback. Upon reaching the lockedposition, the user also preferably realizes a decrease in resistance,thereby knowing that they have reached the correct and final lockedposition.

A second embodiment of the locking mechanism is found in the use of nibsor protrusions 58 which extend proximally and longitudinally from thetail 14 of the nozzle assembly 10. While two nibs 58 are preferred, onemay be used effectively. The nibs 58 are preferably positioned onopposite sides of the tail 14, as shown in FIG. 4. Most preferably, thenibs 58 are positioned at 0° and 180° while the studs 52 are positionedat 90° and 270°. When the tail 14 is inserted into the injector 30, thenibs 58 engage in recesses 60 in the interior of the injector 30. Therecesses 60 may be provided in the retaining element 20 which isdisposed within the injector 30 interior.

It is preferred that, when the tail 14 and rib segments 16 are insertedinto the injector 30 and rotated to turn the rib segments 16 into thegrooves 36, the nibs 58 are slightly depressible and travel along aninternal surface of the injector 30 until they engage the recess 60.

A transverse slot 64 is preferably positioned adjacent the nibs 58. Thisslot 64 allows the nibs 58 to exhibit deformable characteristics. Ifplastic or a similar softer material is utilized for the nozzle assemblybody, it is possible to use the nib 58 without the slot 64. However, inorder to allow the nibs 58 to flex inwardly, it is desirable to providethe slots 64 next to the nibs in order to allow the nibs 58 to flexslightly inwardly until they reach the recess 60. The nibs 58 reach thefinal locked position when they enter the recess 60. When the nibs 58reach the recess 60, the nozzle assembly 10 has been entirely screwedinto the injector 30. As the nibs 58 reach the final locked position 60,the user preferably receives positive feedback that the nozzle assembly10 has been locked in. This positive feedback may be a clicking noise ortactile feedback. Upon reaching the locked position, the user alsopreferably realizes a decrease in resistance, thereby knowing that thecorrect and final locked position has been reached. The nibs 58 arepreferably rounded, which aids in their travel within the injector 30prior to reaching the final locked position.

Both the nibs 58 and studs 52 exhibit sufficient deformablecharacteristics to allow the nozzle assembly 10 to be unscrewed from theinjector 30.

According to a preferred embodiment of the present invention, the nozzleassembly 10 discussed above is formed integrally of metal and preferablystainless steel. This type of nozzle assembly 10 is generally reusable.Another preferred embodiment of the nozzle assembly 10 is formedintegrally of plastic. This type of nozzle assembly 10 is generallydisposable. Other materials can also be used to construct the nozzleassembly 10. A preferred plastic is a polycarbonate such as Makrolon,manufactured by Bayer.

Another feature of the present invention is the use of indicating meansfor properly positioning the nozzle assembly in the injector 30. Thenozzle assembly 10 may preferably include two different indicators 50,66, although it is anticipated that one indicator can be used withoutthe other. The injector 30 should preferably also include anotherindicator 68 which is used in conjunction with the indicators 50, 66 onthe nozzle assembly 10 to properly align the nozzle assembly 10. Theindicator 68 on the injector 30 is located along the rim 70' of theinjector 30 at the distal end. This indicator 68 may be an outwardlyextending tab or protrusion, but is preferably a marking, such as adarkened line or square, as shown in FIG. 3 in phantom. The indicator 68on the injector 30 works in conjunction with the indicators 50, 66 onthe nozzle assembly 10. These indicators 50, 66, 68 are useful becausenozzle assemblies are routinely removed from the body of the injector30. By providing indicators, the nozzle assembly 10 can be easilyaligned for proper insertion into the injector.

There are two types of indicators provided on the nozzle assembly 10.The first indicator 66 may be disposed on one side of the circumferenceof the tail section 14 or preferably on two sides. This indicator may beetched into the nozzle assembly tail 14 or molded into the tail 14 as araised indicator 66. The indicator 66 shown in FIG. 1 is in the form ofan "A", but may be any other type of indicating marking such as a dot.

The second indicator 50, as discussed above, is preferably located onthe transition portion 18 and is disposed at the proximal edge of thetransition portion 18. This indicator 50 preferably extends outwardlyfrom the transition portion 18. As shown in FIG. 6, two secondindicators 50 are preferred, although one may be used. The secondindicator 50 is preferably a tab which extends outwardly from the sideof the transition portion 18.

The first indicators 66 are preferably positioned at the same rotationalangle as the nibs 58 and the second indicators 50 are preferablypositioned at the same rotational angle as the studs 52. Thus, the firstindicators 66 are preferably positioned at 0° and 180° and the secondindicators 50 are positioned at 90° and 270°. However, the spacing ofthe indicators is determined by the difference in position between theengagement or entry point of the nozzle assembly into the injector andthe locking point. Thus, the indicating means can be used independentlyof a locking means, such as the stud and recess. For instance, anindicating means could be used to show the user how to insert a nozzleassembly having bayonet mount teeth into the injector and, afterrotation of the nozzle assembly, can be used to indicate that the nozzleassembly has been fully rotated.

In operation, the first indicator 66 is preferably aligned with theinjector indicator 68 and the nozzle assembly 10 is inserted into theinjector 30. Then the nozzle assembly 10 is rotated in order to engagethe rib segments 16 with the grooves 36 and the locking mechanisms 52,58 with the recesses 54, 60. When the nozzle assembly 10 as beenentirely screwed in such that the locking mechanisms 52, 58 engage therecesses 54, 60, the second indicators 50 ill align with the injectorindicators 68 to indicate to the user that the nozzle assembly 10 hasbeen properly installed on the injector 30.

As discussed above, a retaining element 20 may be used in the injector30 to work in conjunction with the locking mechanisms 52, 58. Aretaining element 20 is desirable because it can be made of a metal,such as stainless steel, while the injector 30 may be made of a softermaterial such as plastic. A metal retaining element provides the lockingmechanisms with a strong surface against which they abut. As such, thisprovides better protection from unexpected disengagement. A metalretaining element is less likely to fail than a conventional plasticinjector body. The metal retaining element is also useful because it canbe readily inserted into an injector 30 with a limited amount ofmodification to the injector 30. The retaining element 20 is shown inperspective in FIG. 2. and in elevated views in FIGS. 8 and 9.

The retaining element 20 is preferably a cylindrical body having adistal end 22 and a proximal end 24. As shown in FIG. 3, the retainingelement 20 is preferably secured near the distal end of the injectorbody. The retaining element 20 may be secured within the injector 30 bypositioning it behind an annular ridge 26 within the interior of theinjector 30. The power unit 32 is then located proximally from theretaining element 20. The nozzle assembly tail 14 may be inserted intothe distal end 22 of the retaining element 20. Therefore, the retainingelement 20 is preferably sized to accept the tail portion 14 of thenozzle assembly 10.

A wall 28 is preferably located at the proximal end 24 of the retainingelement 20. The wall 28 preferably includes an opening 70 for receivingthe piston 72 (shown in FIGS. 14 and 15) of the injector 30, as shown inFIGS. 10 and 11. The piston 72 accepts energy from the power unit 32 todrive the medicament out of the internal chamber 40 of nozzle assembly10. Thus, the opening 70 in wall 28 is sized to accept the diameter ofthe piston 72.

The wall 28 also includes at least one recess or groove 60 for acceptingthe second locking mechanism, the nib 58. As shown in FIGS. 10 and 11,the grooves 60 runs perpendicular to the longitudinal axis X--X of theretaining element 20 in wall 28. As shown in FIGS. 2, 8 and 9, retainingelement 20 includes apertures 65 to facilitate matching of grooves 60.The grooves extend from the outer circumference of the retaining element20 to the opening 70 in the wall 28. When two nibs 58 are used on thenozzle assembly 10, the grooves 60 are preferably asymmetrical orradially offset from the center line of opening 70. The grooves 60 areasymmetrical to provide a sharp drop off for entry of the nib 58 intothe groove 60. The grooves 60 are preferably rotated 180° relative toeach other on wall 28 to accommodate nibs 58, which are also preferablyrotated 180° relative to each other. However, if nibs 58 are notpositioned at 180° relative to each other, grooves 60 will preferably beat the same radial angles as nibs 58.

The retaining element 20 also includes a recess 54 for receiving thefirst locking mechanism, the stud 52. This second recess 54 ispreferably in the shape of a substantially L-shaped slot. A firstopening 72' of the slot extends axially from the distal end of theretaining element partially along the length of the retaining element20. A second opening 74 of the slot 54 extends from the end of the firstslot at an angle K in a helix pattern. This angle K is preferably thesame pitch and angle β as the partial helix of the rib segments 16 ofthe nozzle assembly 10. The angle K allows stud 52 to travel axially atthe same rate as the rib segments 16. A detent 56 is located at theother end of the second opening 74 for receiving the stud 52 in thelocked position.

In use, when both the stud 52 and nibs 58 are utilized on the nozzleassembly 10, the nozzle assembly 10 is inserted into the injector 30 andretaining element 20 such that the stud 52 aligns with the first opening72' of the L-shaped slot 54. When the nozzle assembly 10 has been fullyinserted longitudinally into the retaining element 20, it is rotated inorder to rotate the rib segments 16 of the bayonet into thecorresponding grooves 36 in the injector 30, as shown in FIG. 3. Thesecond opening 74 of slot 54 is preferably dimensioned such that a lightinterference fit occurs between the nozzle assembly 10 and retainingelement 20 as the rib segments 16 are rotated into grooves 36. As thenozzle assembly 10 is rotated, the stud 52 travels along the secondopening 74 of the L-shaped slot 54 until it enters the detent 56. Whenthe stud 52 enters the detent 56, the nozzle assembly 10 should be fullyrotated so that the rib segments 16 and grooves 36 have engaged. Whenthe stud 52 reaches the detent 56, the user preferably encounters aclicking noise or a tactile sensation signalling to the user that thestud 52 has entered the detent 56. This tactile sensation will be one ofreduced resistance. Once the stud 52 is located in the detent 56, thefirst locking mechanism 52 is engaged and will deter the nozzle assembly10 from disengaging during firing of the injector 30. In addition toproviding a locked position, the L-shaped slot helps to insure that thenozzle assembly is properly inserted and positioned in the injector.Thus, the L-shaped slot also helps to deter improper engagement of thenozzle assembly in the injector.

As for the second locking mechanism 58, when the nozzle assembly 10 isrotated in the retaining element 20 to engage the rib segments 16 withthe grooves 36 in the injector 30, the nibs 58 encounter resistanceagainst the inner side of wall 28. As the rib segments 16 are turnedfurther, this resistance increases. When the slot 64 is provided in thetail 14 of the nozzle assembly 10 adjacent the nibs 58, the nibs willdeform slightly inwardly enough to allow the nozzle assembly 10 to befully rotated into the retaining element 20 and injector 30. As the ribsegments 16 reach the end of their travel path within the grooves 36,the nibs 58 will enter the recess 60 disposed in the inner side of thewall 28 so that when the nozzle assembly 10 is fully rotated into thefinal position, the nibs 58 will be located in the recesses 60. Thislocking mechanism helps to deter the nozzle assembly 10 from disengagingunexpectedly during firing because the nozzle assembly 10 is deterredfrom rotating. The combination of the two locking mechanism 52, 58 usedsimultaneously, helps to further ensure that the nozzle assembly 10 willnot disengage. This combined with the use of optimized pitch bayonetthreads 16 will further help to deter unexpected disengagement.

FIG. 12 shows a first embodiment of the improved plunger design of thepresent invention. The plunger 80 is typically situated in the internalchamber 40 of the nozzle assembly 10, as shown in FIG. 16. As shown moreclearly in FIG. 21 for a second embodiment of plunger 80, when thenozzle assembly 10 is attached to the injector 30, the plunger 80becomes attached to the piston 72 of the injector 30. The piston 72 isconnected to the power source 32 so that when the power source 32 isfired, the piston 72 moves the plunger 80 distally to expel medicamentfrom the internal chamber 40 through orifice 42.

After the injector 30 has been fired, the plunger 80 moves to the distalend of the chamber 40. In order to recharge the power source and toreplace the nozzle assembly 10, the plunger 80 must be removed from thepiston 72 so that a sterile nozzle assembly may be reinstalled. Aproblem has been found with prior plungers in that they were oftendifficult to remove from the piston 72 after firing so that when thenozzle assembly was removed from the injector 30, the plunger 80remained attached to the piston. As a result, the plungers needed to bemanually removed, such as by force or by destruction. The presentplunger 80 and nozzle assembly 10 designed alleviates this problem byproviding outwardly curved prongs or legs 82 on the plunger 80.

As shown in FIG. 12, the plunger 80 of the present invention includes adistal end and a proximal end. The plunger 80 is preferably cylindricalin shape and is sized to fit snugly, but slideably within the internalchamber 40 of the nozzle assembly 10. The tip 84 of the plunger 80 islocated at the distal end and is preferably shaped to substantiallymatch the internal contours of the internal chamber 40 of the nozzleassembly 10 at its distal end. The plunger 80 preferably includes a seal86 adjacent the tip 84. The seal 86 helps to prevent any medicament frompassing by the seal 86 before or during firing of the injector 30. Theseal 86 is preferably compressed during use in order to provide a tightfit within the internal chamber 40, as shown in FIG. 16.

A plurality of prongs or legs 82 are located at the proximal end of theplunger 80. The prongs 82 are for attaching to piston or ram 72 ofinjector 30. The prongs 82 of the present invention are normallyoutwardly curved or flexed, but are flexible enough to be bend againsttheir normal position so that the plunger 80 may slide within chamber40. As shown in FIG. 14, four prongs 82 are preferred, although anynumber of prongs 82 may be used. A lead portion 88 of piston 72 ispreferably shaped to connect with the plunger prongs 82, as shown inFIG. 21. Each prong 82 includes a lip 90 for encircling the lead portion88 of the piston 72. Each prong 82 is preferably spaced at even anglesaround the outer circumference of the plunger 80. The plunger 80 alsoincludes a post 92 which is positioned along the longitudinal axis X--Xof the plunger 80 centrally between the prongs 82. This post 92 is forcontact with the piston 72 when the power source 32 is fired. When thepower source 32 is fired, the piston 72 moves distally until it contactsthe post 92, at which point the plunger 80 and piston 72 move togetherto expel medicament from the internal chamber 40 through the orifice 42.If the lead portion of the piston 72 is substantially the same length asthe distance between the prong lips 90 and the post 92, the piston 72will not move longitudinally relative to the plunger 80. If the leadportion 88 of the piston 72 is smaller than the length of the distancebetween the lips 90 and the post 92, the piston 72 will movelongitudinally relative to the plunger 80 until it contacts the post 92.

The outwardly curved prongs 82 of the plunger 80 may be shorter inlength than the length of the plunger 80 and extend at the proximal endthereof. Lip 90 is located at the proximal end of the prongs 82, asshown in exploded cross-sectional view in FIG. 13. The proximal end ofprong 82 preferably includes several sloped surfaces. A first slopedsurface 91 is preferably at an angle Δ of about 20°, but may range fromabout 0 to 40°. This sloped surface aids the plunger in disengaging fromthe piston 72. A second sloped surface 93 is preferably at an angle E ofabout 30°, but may range from about 0 to 90°. The second sloped surfaceis provided to aid lead portion 88 in entering the proximal end ofplunger 80 to engage with prongs 82 when a nozzle assembly is insertedinto an injector 30.

FIG. 15 shows a cross-section of plunger 80 at area 15--15. At thislocation, plunger 80 is cylindrical and preferably exhibits a circularcross-section with recesses 81 to form an X or cross shape. At one side,the cross-shaped section has a shortened arm 83 with an outwardlyextending protrusion 85. Since plunger 80 is typically manufactured bymolding, recesses 81 and shortened arm 83 are utilized in the moldingprocess. Recesses 81 are cored out in order to reduce shrinkage of theplunger. Arm 83 is utilized as a connection point to the mold andprotrusion 85 is a point at which the plunger is released from the mold.By providing shortened arm 83, no additional surface finishing of theplunger is required after separation from the mold.

The nozzle assembly 10 internal chamber 40 includes a tapered portion 96at the proximal end for receiving the outwardly curved prongs 82, asshown in FIGS. 5 and 16. This tapered portion 96 is preferablysufficiently tapered to allow the prongs 82 of the plunger 80 to enterthe taper and allow the piston 72 to be released from the plunger 80after firing.

In operation, the plunger 80 rests within internal chamber 40 such thatprongs 82 are compressed inwardly against their outwardly curvedcharacteristic. After the injector 30 is fired, the plunger 80 islocated at the distal end of the internal chamber 40. In order to rearmthe power source 32 and to replace the nozzle assembly 10 for the nextinjection, the piston 72 is withdrawn proximally. As the piston 72 ismoved proximally and as the plunger 80 reaches the outwardly flaredportion 96 of the internal chamber 40, as shown in FIG. 16, theoutwardly curved prongs 82 curve outwardly to assume their relaxedposition and enter the tapered portion 96. Since the prongs 82 areallowed to bend outwardly to their relaxed position, clearance isprovided so that the lips 90 of prongs 82 no longer engage with the leadportion 88 of the piston 72. As a result, the piston 72 is easilywithdrawn from the plunger prongs 82. When the nozzle assembly 10 isunscrewed from the injector 30, the plunger 80 remains within the nozzleassembly 10, thereby alleviating the problem which previously existedwith the plunger 80 failing to release from the piston 72.

The plunger 80 of the first embodiment is preferably constructed of aplastic material, although other materials may be used. Plastic istypically selected where the plunger is disposable. Preferred plasticmaterials include the following polymers: polycarbonate, acrylic,polypropylene and polystyrene.

A second embodiment of plunger 80 is shown in FIG. 17. This plunger 80exhibits many of the same features as the plunger shown in FIG. 12, butalso includes a frangible portion 100. The plunger 80 includes a distalend and a proximal end and is preferably cylindrical in shape and sizedto fit snugly, but slideably within the internal chamber 40 of thenozzle assembly 10. The tip 84 of the plunger 80 is located at thedistal end and is preferably shaped to substantially match the internalcontours of the internal chamber 40 of the nozzle assembly 10 at itsdistal end. The plunger 80 preferably includes a seal 86 adjacent thetip 84.

The seal 86 helps to prevent any medicament from passing by the seal 86before or during firing of the injector 30. The seal 86 is preferablycompressed during use in order to provide a tight fit within theinternal chamber 40, as shown in FIG. 16.

The plurality of prongs or legs 82 are located at the proximal end ofthe plunger 80. The prongs 82 are normally outwardly curved. A leadportion 88 of piston 72 is preferably shaped to connect with the plungerprongs 82 as shown in FIG. 21. Each prong 82 includes a lip 90 forencircling their lead portion 88 of the piston 72. In addition toincluding a lip 90 on their inner surface, prongs 82 include a ridge 94on the external surface. Both the lip 90 and the ridge 94 are located atthe proximal end of prongs 82, as shown in exploded cross-sectional viewin FIG. 18.

Ridge 94 is for associating with an annular groove 98 in tapered portion96 at the proximal end of the nozzle assembly 10, as shown in FIGS.21-23. Groove 98 is preferably located near the widest portion ofoutwardly tapered portion 96 and is sized to receive ridge 94. Thisgroove 98 and ridge 94 help to prevent the plunger 80 from being pushedinto the nozzle assembly 10 before the piston 72 engages post 92. Whensufficient pressure is applied to post 92 by piston 72, the prongs 82will disengage from groove 98 to allow the plunger 80 to move distallyso that prongs 82 and lips 92 engage lead portion 88. Groove 98 alsopreferably includes a sloped proximal edge 99 which is provided tofacilitate manufacturing. Sloped proximal edge 99 is preferably slopedat an angle of θ which is about 45° relative to the longitudinal axisX--X, but angle θ may range from about 0° to 90°.

As shown in FIGS. 17 and 20, plunger 80 of the second embodiment isfrangible. It is known to use a frangible piston, as taught by U.S.patent application Ser. No. 08/608,799, which is incorporated herein byreference. Plunger 80 has a first driving member 110 and a seconddriving member 120. As shown, these members have a generally cylindricalshape with specially shaped base 112, 122 and end portions 114, 124.

While a plunger having a D-shaped end and base portions can be used, itis preferred to use a modified D-shape wherein portions of the arcuatepart of the D 81 have been removed, as shown in FIG. 20. These drivingmembers 110, 120 are connected together in a spaced apart relationshipacross a predetermined gap G by a frangible connection or bridge 100.

As shown in FIG. 17, the preferred frangible bridge 100 is a relativelythin, overlapping and connecting portion of the first and second drivingmembers 110, 120. It is preferred that the height of the frangiblebridge be minimal to provide a localized shear zone. The frangibleportion 100 may be disposed adjacent both straight sides of end portions114, 124 of the first and second driving members 110, 120. A leading ordistal edge 111 of frangible portion 100 is preferably shaped as a sharpcorner. This sharp corner provides stress concentration for assisting inshearing the frangible portion when an appropriate load is applied tothe second driving member 120. A trailing or proximal edge 121 offrangible portion 100 is preferably rounded, defining a radius. Thisradius is defined to provide a clean two-part break which allows thesecond driving member 120 to close the gap G between the first 110 andsecond 120 driving members.

Further, recesses 123 are defined at the end of the channels whichdefine the frangible portion 100. These recesses are positioned in thebase portions 112, 122, adjacent the frangible portion 100, and areconfigured and dimensioned to accept flash or waste which may break awayfrom the frangible bridge 100 during shearing. Recesses 123 are providedin order to avoid any interference between any flash and the movement ofthe first and second driving members 110, 120.

Frangible portion 100 is preferably spaced a small distance fromlongitudinal axis X--X in order to aid in providing a frangibleconnection which will shear when a sufficient amount of force isapplied. Preferably, the plunger 80, including the frangible bridge ismade out of a plastic and is configured and dimensioned such thatfrangible portion 100 can withstand a force "p" for moving orwithdrawing the plunger to draw liquid medication into chamber 40without breaking. Typically, an acrylic polymer will provide thestrength necessary to withstand loading or medication fillingprocedures, but is also sufficiently brittle to break when the firingforce is applied. The present frangible portion 100 is designed to shearwhen force "P," which is greater than force "p" is applied.

Alternatively, the frangible plunger 80 can be used with a prefilledchamber 40, thereby eliminating the need for moving the plunger 80longitudinally to draw liquid medication into chamber 40 or to expelexcess liquid or bubbles therefrom.

The leading end of the first driving member 110 includes the seal 86,such as an O-ring or the like, preferably formed around its outerperiphery to provide a seal with the inner wall of the chamber 40. Theplunger 80 itself can be a seal. Other seals or seal members can beincluded in the trailing end of the second driving member 120 if desiredto provide a better seal to prevent leakage of fluid for the chamber byminimizing the entry of air into the chamber from around the first andsecond driving members 110, 120 and by preventing air from entering theorifice 42 due to liquid exiting the chamber around the driving members.

As part of the filling operation, the plunger 80 is pushed into thechamber 40, in the distal direction to purge air from the internalchamber, as shown in FIG. 21. As the plunger 80 is pulled in theproximal direction, a partial vacuum is established inside the chamberand liquid medication is drawn into the chamber 40 through the orifice42.

It will be noted that the frangible connection is dimensioned andconfigured such that pushing or pulling action requiring force "p"normally affiliated with withdrawal and slow ejection of air ormedication before injection does not break the bridge 100. Upon anapplication of a relatively large injection force "P" on the ram, whichmay be significantly larger than the force "p", the ram transmits thisforce "P" to the second driving member 120 and breaks the frangibleportion 100. This allows the second driving member 120 to close the gapG and transmit force to the first driving member 110 so that therespective base 112, 122 and end 114, 124 portions meet to ejectmedication out of the chamber 40. Specifically, the end portion 114 ofthe second driving member 120 contacts the base portion 112 of the firstdriving member 110 while the base portion 122 of the second drivingmember 120 contacts the end portion 124 of the first driving member 110for urging the first driving member 110 towards the chamber orifice 42to expel fluid therefrom.

FIG. 22A shows the position of the plunger 80 after the injection iscompleted and all the medication has been ejected. In this position, thefrangible connection 100 has been broken so that the first 110 andsecond 120 driving members are in contact and the plunger 80 ispositioned in the distal end of the chamber 40.

Finally, FIG. 22B shows the position of the plunger 80 after theinjection is completed and the nozzle assembly 10 has been rotated orunlocked from the injector. The nozzle assembly has been rotated so thatrib segments 16 are free of the injector 30 and can be removed. At thispoint, as the nozzle assembly 10 is withdrawn or pulled back from theinjector 30, the piston 72 and second driving member 120 move proximallywithin the chamber 40 until the outwardly curved prongs 82 engage theoutwardly tapered portion 96 of the nozzle assembly 10. When thisengagement occurs within the tapered portion 96, the piston 72 is freedfrom the prongs 82 and the nozzle assembly 10 may be completely removedfrom the injector 30. Thus, the first 110 and second 120 driving membersremain inside the nozzle assembly and are easily removed from theinjector 30 and the nozzle assembly 10 then may not be reused and mustbe discarded. This prevents unwanted re-use of the nozzle assembly.

In a normal operation of the injector, piston 72 of the injection deviceoperatively connected to an energy source 32 imparts sudden force orimpact "P" to the second driving member 120, enough to drive the secondmember 120 into the first member 110. This action is sufficient to drivethe liquid contained in chamber 40 outward through orifice 42 as a peakjet stream pressure for example in excess of 5,000 psi out of theorifice 42. This sudden force "P" is capable of breaking the frangiblebridge 100 before the injection begins. Specifically, the force "P"applied to the second driving member 120 is transmitted to the firstdriving member 110 through the bridge 100. Initially, the frictionalforce in the seal 86 generates enough friction to momentarily preventthe plunger 80 from moving. Once this frictional force is overcome, theplunger 80 starts to move and imparts pressure to the medication in thechamber 40. This creates resistance or back pressure on the firstdriving member 110. When the difference between the resistance forceimparted to first driving member 110 by the fluid and the force impartedby the second driving member 120 toward the first driving member 110reaches a predetermined level, the bridge 100 breaks and the seconddriving member 120 rams into the first driving member 110.

Alternatively, frangible bridge 100 may be broken by an intermediateforce larger than the force "p," before the relatively large injectionforce "P" is applied to piston 72. Such an intermediate force can begenerated for example by a pressure exerted on the liquid contained inchamber 40 through orifice 42 or by other triggering mechanism.

The gap "G" plays an important role in creating a preferred pressurespike necessary to pierce through the patient's skin. Changing the gap Gwill change the initial force imparted on the first driving member 110.The peak pressure thus can be varied with the gap G. It can also varydepending upon the viscosity of the medication, the desired injectionpenetration depth, and other parameters which may affect the initialinjection pressure output. One of ordinary skill in the art candetermine by routine experimentation the optimum gap for any frangibleplunger that is to be used with a particular medication. Advantageously,frangible plunger 80 or nozzle assembly 10 or both can be manufacturedwith different colors, wherein each color denotes a predetermined widthof gap G. This color coding scheme will assist the user in choosing aproper nozzle assembly 10 for a specific application. In addition, theamount of force to break the bridge 100 can be adjusted by changing thedimension of the bridge 100.

It will be understood that the frangible plunger according to thepresent invention can also be used with syringes having hypodermicneedles where the frangible bridge breaks either before the injectionbegins or after the completion of the injection. It will also beunderstood that a plunger with the outwardly curved prongs may beutilized without a frangible portion.

While various features of the present invention were described above, itis understood that the various features of the present invention can beused singly or in any combination thereof. Therefore, this invention isnot to be limited to only the specifically preferred embodimentsdepicted herein.

Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains. Accordingly, all expedientmodifications readily attainable by one versed in the art from thedisclosure set forth herein that are within the scope and spirit of thepresent invention are to be included as further embodiments of thepresent invention. The scope of the present invention is accordingly tobe defined as set forth in the appended claims.

What is claimed is:
 1. A plunger slidingly movable within a fluidchamber for expelling fluid out of or drawing fluid into the chamber bymoving the plunger relative to the chamber, the plunger comprising firstand second driving members which include respective end and baseportions retained in spaced relation by a frangible connectiontherebetween, with the second driving member being spaced apart from thefirst driving member by a gap, such that when a force sufficient tobreak the frangible connection is applied to the second driving memberin a direction toward the first driving member, the frangible connectionis broken and the second driving member moves across said gap toward thefirst driving member for urging the first driving member towards an endof the chamber to expel fluid therefrom, and when the second drivingmember is thereafter moved away from the first driving member, the firstdriving member remains in the chamber to prevent reuse of the plunger.2. The plunger according to claim 1, further comprising means forconnection to a force generating component.
 3. The plunger according toclaim 2, wherein the connection means comprises a plurality of outwardlyflared prongs.
 4. The plunger according to claim 1, wherein the plungeris cylindrical and the first and second driving members meet to definethe frangible connection therebetween, said frangible connection havingat least a portion which extends across the diameter of the plunger. 5.The plunger according to claim 1, wherein the first driving member has aseal in contact with the chamber.
 6. The plunger according to claim 1,wherein the frangible connection is disposed perpendicular to the planesformed by the surfaces of the end portions of the first and seconddriving members.
 7. The plunger of claim 1, wherein the frangibleconnection is spaced radially relative to the longitudinal axis.
 8. Theplunger of claim 1, wherein the chamber includes a tapered portionadjacent the orifice and the first driving member includes a taperedmember which conforms to the tapered portion of the chamber.
 9. Theplunger of claim 1, wherein the end and base portions of the first andsecond driving members face each other and are joined by the frangibleconnection.
 10. The plunger of claim 9, wherein the first driving memberis separated from the second driving member by a gap, and the frangibleconnection extends from the second driving member to connect the endportions of the first and second driving members, such that when a forcesufficient to break the frangible connection is applied to the seconddriving member, the frangible connection is broken and the seconddriving member moves across the gap toward the first driving member withthe base portion of the second driving member contacting the end portionof the first driving member as the end portion of the second drivingmember contacts the base portion of the first driving member for urgingthe first driving member towards the end of the chamber.
 11. The plungeraccording to claim 10, wherein when the second driving member isthereafter moved away from the first driving member, the first drivingmember remains in the chamber to prevent reuse of the plunger.
 12. Theplunger of claim 10, wherein each of the end portions is configured anddimensioned to occupy more than half the cross-sectional area of theplunger, wherein the first and second end portions are positioned insubjacent relation after the second member moves across the gap.
 13. Aplunger slidingly movable within a fluid chamber having proximal anddistal ends with an outwardly flared portion adjacent the proximal endthereof, which plunger comprises:a body member having a distal end and aproximal end, said distal end for expelling fluid out of or drawingfluid into the chamber; and a plurality of outwardly flared prongslocated at the proximal end of the plunger, said prongs beingoperatively associated with a force generating component for movement ofthe body member and being configured and dimensioned to be received inthe outwardly flared portion of the chamber in order to allow release ofthe force generating component from the prongs without removing theprongs from the chamber.
 14. The plunger of claim 13, wherein theoutwardly flared prongs have an inner surface and an outer surface and alip portion is located on the inner surface.
 15. The plunger of claim14, wherein the outwardly flared prongs have a ridge portion positionedon the outer surface and said outwardly flared portion of the internalchamber includes an annular groove for receiving the ridge portion. 16.The plunger of claim 14, wherein the force generating component includesa lead portion and the lip portions of the prongs engage the leadportion when the prongs are positioned within the chamber.
 17. A nozzleassembly adapted for use with an injection device comprising:a chamberfor holding a fluid and having an orifice for fluid passage at one end;a force generating component for generating a force to expel fluid outof or to draw fluid into the chamber; and the plunger of claim
 2. 18. Anozzle assembly adapted for use with an injection device comprising:achamber for holding a fluid and having a proximal end, a distal end, anoutwardly flared portion adjacent the proximal end, and an orifice forfluid passage at the distal end; a force generating component forgenerating a force to expel fluid out of or to draw fluid into thechamber; and the plunger of claim
 13. 19. The nozzle assembly of claim17, wherein the plunger is made of an acrylic polymer.
 20. The nozzleassembly of claim 18, wherein the plunger is constructed of a materialwhich includes a polymer selected from the group consisting ofpolycarbonate, polypropylene, polystyrene, and acrylic.